1. Field of the Invention
The present invention relates to a front transaxle device of a multi-wheel-drive vehicle.
2. Background Art
Conventionally, a multi-wheel-drive vehicle wherein four or more wheels are driven is known.
In this multi-wheel-drive vehicle, transaxle devices for supporting axles are disposed corresponding to the positions of the axles. For example, a rear transaxle device for supporting rear axles is disposed at a rear portion of the vehicle, and a front transaxle device for supporting front axles is disposed at a front portion of the vehicle. In a structure where six or more wheels are driven, a middle transaxle device for supporting middle axles is disposed at a longitudinally intermediate portion of the vehicle.
Furthermore, a transmission which transmits the power from a prime mover (e.g., an engine) is provided. By transmitting the power from the transmission to each of the transaxle devices, the wheels are driven through each of the axles.
In comparison with a two-wheel-drive structure, the above-mentioned multi-wheel-drive structure is more useful in that its driving performance over a bad road is good, and plenty of power is available for climbing a hill. Thus, this structure has come to be widely adopted by various kinds of vehicles such as automobiles, agricultural trucks, and the like.
Now, further improvement of such a multi-wheel-drive vehicle in terms of its driving performance over bad roads, cost-saving, maintainability, etc., is increasingly desired given the increasing popularity of such vehicles.
An object of the invention is to provide a front transaxle device which gives improved braking performance to a multi-wheel-drive vehicle so as to improve further the driving performance of the vehicle over bad roads. Another object of the invention is to provide the front transaxle device with a simple structure so as to reduce manufacturing costs and enhance the maintainability thereof.
According to the present invention, a front transaxle device provided to a multi-wheel-drive vehicle comprises an input shaft for receiving power, a pair of left and right front axles supported in the front transaxle device, a differential connecting the left and right front axles in a differential manner, a pinion shaft, a clutch device which engages the pinion shaft with and disengages the pinion shaft from the input shaft, a rotary object interposed between the differential and the pinion shaft, and a brake device which brakes the rotary object. Therefore, the braking performance is improved and the vehicle""s braking distance can be shortened. Thus, a multi-wheel-drive vehicle, which can run smoothly on a bad road and enhance fuel economy, may be available. Furthermore, by operating the clutch device, it is easy to select between the mode wherein the power is transmitted to the front wheels supported by the front transaxle device and the mode wherein the power is not transmitted to the front wheels. Thus, by linking the clutch device with operating means, a vehicle which can be put between 4-wheel-drive mode and 6-wheel-drive mode (for example) is available. Additionally, because the clutch device is disposed between the input shaft and the pinion shaft and the brake device is disposed at the rotary object, the two devices are separated and can avoid interfering with each other, thereby reducing the complexity of the layout.
The brake device comprises a piston which can be moved hydraulically, friction objects which engage with each other by the force of the piston, and a mechanism which maintains a constant stroke of the piston to engage the friction objects regardless of any abrasive reduction of the friction objects. Therefore, in spite of abrasive reduction of friction objects in the brake device, it is unnecessary to adjust the stroke of the piston to keep a good braking response of the brake device, thereby reducing the need for maintenance.
The rotary object is a middle shaft disposed between the pinion shaft and the differential and supported parallel to a rotational axis of the differential, and the middle shaft is engaged with the differential through a spur gear. Therefore, the parts of the brake device are arranged along and detached from the middle shaft parallel to the rotational axis of the differential. Thus, installation and removal of the brake device is easy, thereby resulting in good maintainability. Furthermore, because the middle shaft is connected with the differential through the spur gear, realignment using a shim and the like, which is necessary in a structure having the middle shaft connected with the differential through bevel gears, is not necessary. Such alignment can be eliminated.
A front transaxle device is provided to a multi-wheel-drive vehicle which has six or more wheels, wherein a pair of foremost wheels of the vehicle are supported and can be driven. A transmission provided to the vehicle is connected with the front transaxle device through a clutch device which is engaged when a brake operating means provided to the vehicle is operated to brake. Therefore, when the brake operating means is operated to its braking position by the linkage between the brake operating means and the clutch device, braking force is also transmitted to the pair of foremost wheels. Thus, the vehicle""s braking distance at high speed can be shortened. Additionally, the front transaxle device can be bypassed when the brake device is not being operated, thereby enhancing fuel economy.
Other and further objects, features, and advantages of the invention will appear more fully from the following description.